1. Field of the Invention
The present invention relates to an apparatus and method for producing trichlorosilane in which metallurgical grade silicon powder is reacted with hydrogen gas and silicon tetrachloride gas (STC) while being fluidized by the hydrogen gas and STC, thereby producing trichlorosilane.
2. Description of Related Art
Trichlorosilane (SiHCl3) used as a raw material for producing high purity silicon may be produced by reacting metallurgical grade silicon powder (Si) of about 98% purity with STC and hydrogen gas.
The apparatus for producing trichlorosilane includes a reactor, a raw material supply device for supplying metallurgical grade silicon powder to the reactor, and a gas introduction device for introducing hydrogen gas and STC with which metallurgical grade silicon powder is reacted. In the apparatus, the metallurgical grade silicon powder inside the reactor is reacted with hydrogen gas and STC while being fluidized with the hydrogen gas and STC, and the generated gas containing trichlorosilane is discharged from the upper part of the reactor. Conventionally, a heat transfer tube extending vertically in the reactor through which a process gas is heated in a tortuous path is provided inside the reactor. Such heat transfer tube is heated externally by vertical carbon heating elements. The heat transferred to the process gas travels though the vertical tube and is therefore indirectly heated. The heat transfer tube is difficult to scale as increases in size place greater stress on the carbon parts of the tortuous path.
However the typical vertical tube heater design has a limited contact surface for heat transfer and as a result must have a different heating profile in order to achieve desired reaction temperature inside the reactor. Heat loss due to indirect heating and a limited contact surface for heat transfer can be inefficient depending on the scale of the reactor.
In order for the conversion reaction to take place, the feed gas must be heated from about 450° C. to greater than about 600° C. At these temperatures carbon heaters suffer from radiant and convective heat loss. Carbon heaters can also be prone to mechanical failure by cracking.
The desire for improving the heat transfer coefficient in a well-insulated reactor lead to the invention herein.